<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    .top {
      height: 100px;
      width: 100%;
      background-color: #0fc;
    }

    .footer {
      height: 100px;
      width: 100%;
      background-color: #acf;
    }

    .main {
      height: calc(100vh - 200px);
      display: flex;
    }

    .left {
      background-color: rgb(228, 126, 228);
      width: 100px;
      overflow: auto;
    }

    .right {
      background-color: rgb(212, 245, 25);
      flex: 1;
      overflow: auto;
    }
  </style>
</head>

<body>
  <div class="top"></div>
  <div class="main">
    <div class="left">
      <p>1</p>
      <p>2</p>
      <p>3</p>
      <p>4</p>
      <p>5</p>
      <p>6</p>
      <p>7</p>
      <p>8</p>
      <p>9</p>
      <p>10</p>
      <p>11</p>
      <p>12</p>
      <p>13</p>
      <p>14</p>
      <p>15</p>
      <p>16</p>
      <p>17</p>
      <p>18</p>
      <p>19</p>
      <p>20</p>
    </div>
    <div class="right">
      <p>1</p>
      <p>2</p>
      <p>3</p>
      <p>4</p>
      <p>5</p>
      <p>6</p>
      <p>7</p>
      <p>8</p>
      <p>9</p>
      <p>10</p>
      <p>11</p>
      <p>12</p>
      <p>13</p>
      <p>14</p>
      <p>15</p>
      <p>16</p>
      <p>17</p>
      <p>18</p>
      <p>19</p>
      <p>20</p>
    </div>
  </div>
  <div class="footer"></div>
</body>

</html>